Silver Sintering Heat Sink Assembly with Mold Module

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Solution Overview

Problem

Existing pressure sintering methods face issues with untested substrate units causing yield losses and deformation due to thermal expansion mismatches, leading to inefficient heat transfer and increased costs from excessive mold compound usage.

Innovation Solution

The process involves pre-testing substrate units, shaping them into a robust mold module, and using a thermosetting cover compound with a coefficient of expansion matched to the ceramic substrate, allowing for silver sintering with a heat sink plate, which is then press-molded to prevent deformation and reduce mold compound usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If untested substrate units are used in pressure sintering, then manufacturing cost is reduced, but yield loss increases due to defective units

Engineering Contradiction:

Improvemanufacturing costVSAvoidyield

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent implements preliminary electrical testing of substrate units before assembly into the final module. This preliminary action identifies defective units early in the manufacturing process, allowing them to be discarded before costly pressure sintering operations. The testing step is performed on individual substrate units with mounted semiconductor components, ensuring only functional units proceed to the sintering process with the heat sink plate.

Inventive Principle:

Principle #10Preliminary action

2Adaptability or versatility

If substrate units with different coefficients of expansion are assembled together, then design flexibility is improved, but deformation occurs due to thermal expansion mismatches

Engineering Contradiction:

Improvedesign flexibilityVSAvoiddeformation

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent explicitly addresses thermal expansion mismatches by selecting and arranging substrate units and heat sink plates based on their coefficients of thermal expansion. The method groups substrate units with similar expansion characteristics together and positions them adjacent to heat sink plates with matching expansion coefficients. This strategic arrangement minimizes differential thermal stress during the pressure sintering process and subsequent thermal cycling, preventing deformation while still allowing design flexibility through selective material pairing.

Inventive Principle:

Principle #37Thermal expansion

3Stability of the object's composition

If excessive mold compound is used to prevent deformation, then structural stability is improved, but material consumption and cost increase

Engineering Contradiction:

Improvestructural stabilityVSAvoidmold compound consumption

Core Design Contradiction:

Stability of the object's compositionVSLoss of substance

Solution Approach 1:

The patent changes the approach from using excessive mold compound to controlling and optimizing the amount of mold compound used. By implementing preliminary testing to eliminate defective units and by strategically arranging substrate units with matched thermal expansion coefficients, the patent reduces the need for excessive mold compound as a compensatory measure. The mold compound is applied in controlled amounts just sufficient to provide structural stability and environmental protection, rather than using large excess quantities to prevent potential deformation from unknown defects or thermal mismatches.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This method ensures reproducible convex deformation of the heat sink plate, reduces material and energy consumption, and enables efficient heat transfer by optimizing the heat sink plate's size and thermal conductivity, while allowing for cost-effective and reliable assembly of multi-substrate modules on a single heat sink plate.

Implementation Method 1

renewed heating to approx. 170° C.-200° C. is carried out (thermal activation of polymer cross linking)

Methodology Applied

Scientific EffectThermal activation of polymer cross linking: Photopolymerisation

Implementation Method 2

the thermal conductivity of the heat spreading plate is improved and its dimensions are increased relative to the substrate. This leads to an advantageous thermal resistance (Rth)

Methodology Applied

Scientific EffectHeat conduction: Conduction (thermal)

Implementation Method 3

The substrates consist of a core of aluminum oxide or aluminum nitride having coefficients of expansion of 7-8 ppm/K and approx. 4 ppm/K

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 4

silver pressure-sintering technology of the unprotected semiconductor to a primary circuit support

Methodology Applied

Scientific EffectPressure sintering: Sintering

Data Source

PatentUS8118211B2Method for the low-temperature pressure sintering of electronic units to heat sinks

Publication Date: 2012.02.21 DANFOSS SILICON POWER GMBH

AI summary

A method for the low-temperature pressure sintering of at least one electronic unit to be contacted thermally, firmly connected mechanically, and located on a substrate, comprising the following steps: pressing the electronic unit using a mold enveloping matrix while sparing a connecting surface of the substrate for a heat sink connection, providing a heat sink plate, applying a sintering connecting layer onto the spared region of the connecting surface and/or onto to the region of the heat sink plate provided for contacting, and bonding of the heat sink plate to the substrate of the electronic unit in the region of the connecting surface using silver low-temperature pressure sintering technology.